GB416590A - Improvements in and relating to the manufacture of cellulose ethers - Google Patents

Abstract

Methyl celluloses are produced by treating semi-moist alkali cellulose at a temperature below 10 DEG C., and preferably between 0 and 5 DEG C. with dimethyl sulphate in amount less than one molecular proportion, preferably \ba1/4\be molecular proportion, of dimethyl sulphate for every unit of cellulose treated. The ethers are insoluble in water and do not form substantially complete solutions in aqueous alkalies in any concentration at ordinary temperatures, but they yield solutions when they are suspended in an aqueous solution of sodium hydroxide, cooled to below 0 DEG C. until crystals of ice appear, and then thawed. The concentration of the caustic soda is preferably 8--10 per cent, and that of the methyl cellulose, 5 per cent. The solutions may be used in the manufacture of films and filaments, in filling cloth, bookbinding, textile finishing, and the like. The methyl celluloses may be dissolved also in cuprammonium solutions, solutions of zinc chloride, calcium thiocyanate, and the like. Again they may be dissolved in aqueous caustic soda with the help of colloids or dispersing agents, such as turkey red oil, isopropylated naphthelene sulphonate, and water-or alkali-soluble hydroxyethyl celluloses or methyl celluloses. The methyl celluloses may also be dispersed in a colloid mill with or without the help of dispersing agents. In an example, 216 parts of a -wood boards after conversion to alkali cellulose and ageing, are stirred with 80 parts of dimethyl sulphate at 4--6 DEG C. The product, with or without separation by means of sulphuric acid, is placed into a solution of caustic soda and cooled to about -10 DEG C. until ice crystals appear. When thawed a clear solution is obtained. In another example, the alkali cellulose is aged for a layer period and 40 parts of dimethyl sulphate are employed. In a further example, 216 parts of sulphite wood boards are mercerised with or without ageing, shredded, and treated at 0--5 DEG C. with 33 parts of dimethyl sulphite. The product is brought into solution by twice freezing and allowing to thaw in a solution of caustic soda. Specification 374,964 is referred to.